1. Field of the Invention
This invention relates to shelf-stable filled pasta and methods of manufacturing same. More particularly, the invention relates to partially or fully cooked filled pasta of intermediate moisture in which the pasta shell is rendered shelf-stable by incorporation of or treatment with edible acids and the filling is rendered shelf-stable by means of water activity depressants and microwave or radio frequency treatment.
2. Description of Related Art
Many partially and fully cooked packaged pastas are disclosed in the prior art. Prior methods for rendering them storable include canning, complete or partial drying, freezing or refrigeration, and acidification. These methods, however, produce filled pasta with sensory attributes that are significantly different from freshly made filled pasta.
Fully cooked canned pasta, which generally has more than 38 percent moisture, tends to be soggy and mushy because the moisture difference between the core and surface portion of the pasta is lost. When pasta is first made, the core is less moist than the surface of the pasta. This moisture difference is responsible for the desired xe2x80x9cal dentexe2x80x9d texture. Within hours, however, the moisture difference disappears and the pasta becomes soggy and mushy.
Some workers in the field have resorted to drying the pasta to increase shelf stability. The drying process, however, normally requires careful control of temperature and humidity, takes a considerable amount of space, and must be done very slowly (6-18 hours). If hastened, a hard xe2x80x9cskinxe2x80x9d forms over the surface of the individual pasta pieces, and this skin cracks during subsequent drying. The result is pasta that is fragile and, when prepared for consumption in boiling water, falls apart. Drying can also result in microbiological contamination because the moist warm atmosphere of the dryers encourages microbiological growth. Furthermore, while the bacteria themselves may be rendered harmless by the heat during the final stages of drying, heat stable toxins are often produced that cannot be easily rendered harmless. Finally, dried pasta must be re-hydrated by immersing it in boiling water or steam. This takes a relatively long time and exacerbates the flavor loss already occasioned by the extended drying in filled dried pasta, often the filling does not rehydrate fully and uniformly during cooking.
Others have attempted to reduce the water activity in pasta by adding water activity depressants such as sugars, salts, glycerol, propylene glycol and the like. Adding large amounts of water activity depressants, however, can harm the flavor and texture of the pasta, especially the shell portion of the filled pasta and especially if water depressants are the only means used to obtain pasta that need not be refrigerated or frozen.
Others have attempted to increase shelf stability by adding edible acids to the filling and shell portion pasta to obtain a pH of around 4.6. These bacteria-killing acids, however, result in an unpleasant acid taste, especially when the filling is acidified. As U.S. Pat. No. 5,922,381 to Nestec states, xe2x80x9cin the case of filled pasta products such as ravioli and tortellini, most fillings accentuate the acidic note and the products become almost inedible at pH lower than 4.6.xe2x80x9d To counter the acidic note, others have added basic compounds to sauces in separate packages to neutralize the acids just before eating. In the case of filled pastas, however, the sauce fails to reach the filling, neutralizing only the acid near the exterior of the pasta shell.
It can be appreciated from examining the prior art that there exists a continuing need for a new and improved fully or partially cooked shelf-stable filled pasta that needs no refrigeration or freezing to prolong shelf stability, and methods of making the same. In this regard, the present invention substantially fulfills this need. As used hereafter, xe2x80x9cshelf-stablexe2x80x9d is intended to mean stable at ambient (room temperature) conditions in the absence of refrigeration and/or freezing.
The inventive method of making shelf-stable filled pasta comprises providing an acid-treated or acid-containing fillable pasta piece having an equilibrium pH of about 4.6 or less; inserting filling into the fillable pasta piece to form a filled pasta piece; exposing the filling in the filled pasta piece to microwave or radio frequency radiation to reduce the water activity (Aw) in the filling to about 0.85 or less; sealing the filled pasta piece in a package; and pasteurizing the filled pasta piece at least once at any point in the process after the filling has been inserted into the fillable pasta piece.
Preferred embodiments of the inventive method include some or all of the following features: the fillable pasta piece is formed by first laminating uncooked pasta dough; the filled pasta piece is pasteurized with steam before being exposed to microwave or radio frequency radiation; the sealing entails flushing the package with a gas that contains nitrogen and substantially lacks oxygen; an additional pasteurizing step may occur after the sealing step; the filled pasta piece is a tortellini or a ravioli; and/or the acid-treated, fillable pasta piece is treated with or contains an edible acid, especially those selected from the group consisting of citric acid, lactic acid, fumaric acid, tartaric acid, malic acid and glucono delta lactone.
The inventive shelf-stable filled pasta comprises a pasta produced by the foregoing method. Preferred embodiments of the inventive shelf-stable filled pasta comprise a pasta produced by methods having some or all of the foregoing preferred features.